The present invention relates generally to disk drive systems, and more specifically to an apparatus providing particulate filtration and contamination control in such systems.
With the advent of magnetoresistive (MR) head technology and increasingly lower flying heights, microcontamination has emerged as one of the disk drive industry""s major concerns. Microcontamination in disk drives can occur in a variety of forms, including particles, humidity, corrosive vapors, and organic gases. Sources of contaminants can be found both in internal components and the external environment where the drives or components are assembled or operated.
Concerns about humidity were initially centered upon its impact on stiction. More recently its facilitation and acceleration of corrosion have garnered the attention of disk drive manufacturers, for a number of reasons. Corrosion susceptibility has increased for the thinner magnetic and protective layers within the advanced MR and giant magnetoresistive (GMR) head designs. Smoother disks that are associated with near-contact recording have also increased sensitivity to humidity and organic contamination. Higher operating temperatures associated with higher RPM drives have increased the concentration levels of contaminants outgassing from the internal components.
Controlling particles is important for preventing head crashes and media corruption. Recent efforts have also focused on preventing thermal asperities. Reduction in flying heights, as well as the use of certain head designs and media composites has made controlling particles even more crucial. Any inclusion of contaminants such as dust or other particles may cause damage to the disk surfaces if trapped between the disk surfaces and the slider, which is aerodynamically supported at a minute distance above the disk surface. Any solid contaminants trapped between the slider and this disk surface may score, scratch or damage the disk recording surface, destroying the ability of the disk to record or retrieve data reliably at that location (e.g., thermal erasure), and can lead to a head crash. While efforts to eliminate particles within the disk drive are made during assembly, aging and use of the disk drive typically will result in subsequent deterioration of some components and additional contaminant particles being present in the disk drive.
In order to address the contaminant problem in disk drives, particle and adsorption filters have been developed in order to capture and control contaminants. Carbon adsorption filters are commonly employed to reduce hydrocarbons, and other contaminants like acrylic acid and sebacate. Activated carbon and silica gels are used for humidity control.
The two main types of particle filtration devices typically employed within disk drives are breather filters and recirculation filters. To enable the breather filter to be effective in filtering the air coming into the drive, it needs to be the lowest pressure drop path into the drive. In other words, the air must go through the breather filter instead of bypassing it and entering the drive through another unfiltered leak path. Thus, one needs either a drive that has good seals and a very low leakage rate or a low pressure-drop breather filter. Since it typically costs more to seal a drive well, a breather filter with a lower pressure drop is the usual choice. This is particularly important when using adsorbent breather filters, which can have pressure drops that are higher than ambient particle breather filters.
Recirculation filters remove particulates from the air as the spinning disks rotate the air and therefore particles inside the drive. Particle capturing efficiency, resistance to airflow (i.e., air not flowing through the filter remains unfiltered), and filter locations are important in cleaning the air. Resistance to airflow can be affected by the media, but also by the size of the filter or the number of filters used.
Recent high-RPM disk drives use shrouding almost completely around the disk pack in order to reduce power consumption and to reduce disk flutter. Unfortunately, drives with near fully shrouded disk packs typically do not allow for convenient placement of a recirculating type filter (e.g., in a corner of a base casting). Instead, the filters currently employed within shrouded disk packs are complex, bulky devices which are not very effective, since they are not in the optimal recirculation path. As a result, particles generated by the head-disk interface, particularly for disks within the disk pack, are not easily intercepted by the poorly located recirculation filters. In fact, the movement of the air within the disk pack will entrain and circulate the contaminant particles and significantly raise the probability of disk damage. Finally, these filtering approaches consume significant space and increase the complexity of the disk drives, thus preventing or defeating extensive efforts to reduce power consumption of the drive motors.
As a result, there is a need within the disk drive industry for more effective contaminant control in low flying height disk drives, especially in high RPM drives which employ shrouding to reduce power consumption and reduce disk flutter.
The present invention provides an apparatus for particulate filtration and contamination control in a disk drive system. The present invention accomplishes this goal by providing one or more contaminant collectors attached to the actuator arms in a disk drive. During drive operation, the contaminant collectors capture airborne particles and other contaminants that can potentially damage and interfere with the normal operation of the disk drive.
More specifically, the present invention provides an actuator assembly for supporting a magnetic head in a disk drive. The actuator assembly includes an actuator body having at least one actuator arm connected thereto. Each actuator arm includes at least one contaminant collector operably attached to the arm.
In one embodiment, each actuator arm has one or more cutouts extending through the arm into which a contaminant collector is mounted. In one embodiment, the contaminant collector is made of a porous material, allowing the passage of air through the collector, while trapping airborne contaminant particles. In an exemplary embodiment, the actuator arms are aerodynamically shaped to create a pressure differential between the top and bottom surfaces of the collector during operation, resulting in increased airflow though the collector.
In one embodiment, the contaminant collector is made of a thin, porous planar plastic film, having the capability of capturing airborne particles having a diameter greater than approximately 0.025 micron. In alternative embodiments, the porous contaminant collector is made of an expanded polyvinyl chloride (PVC) plastic, a micro porous polymer of cellulose ester formed around a polyester web, an electret material, or a fibrous material, such as wool or plastic. In another embodiment, the contaminant collector is made of a conductive material that is actively maintained at a predetermined electric potential by a voltage source. The contaminant collector may also be made of an adsorbent material, such as carbon impregnated plastic. Finally, the contaminant collector may incorporate the combination of two or more of the contamination control elements described above.
In yet another embodiment, the contaminant collector is applied to the surfaces of the actuator arm. In this instance, the collector may operate in conjunction with the embodiment of the contaminant collector described above (i.e., the porous filter mounted in the arm cutouts), or may employed alone. In this embodiment, the collector traps particles that come in contact with it. In an exemplary embodiment, this contaminant collector is an inert oil. In alternative embodiments, the contaminant collector is an electret material, or a sticky, non-outgassing adhesive.
In another aspect, a hard disk drive includes a plurality of magnetic storage disks disposed coaxially with respect to each other. An actuator body is positioned adjacent to the disks and is movable relative thereto in response to a control signal. Also, a plurality of transducers are juxtaposed with the storage disks for data transfer therebetween. One or more actuator arms are connected to the actuator body, with each actuator arm including a head-suspension assembly end for holding one or more transducers. Per the present invention, the actuator arms further include at least one contaminant collector operably attached to the at least one actuator arm.
In still another aspect, a digital processing apparatus includes a computer, a plurality of magnetic storage disks disposed in the computer coaxially with respect to each other, and an actuator body positioned adjacent the disk and movable relative thereto in response to a control signal. Also, the apparatus includes a plurality of transducers that are juxtaposed with the storage disks for data transfer between the disks and the computer. Furthermore, the apparatus includes a plurality of actuator arms that are connected to the actuator body, with each actuator arm including a head suspension assembly end distanced from the body for holding one or more transducers. Per the present invention, the actuator arms further include at least one contaminant collector operably attached to the at least one actuator arm.
The details of the present invention, both as to its structure and operation, can best be understood in reference to the accompanying drawings, in which like reference numerals refer to like parts.